In healthy conditions, articular cartilage forms a smooth surface between articulating bone ends to reduce the friction caused by movement. This friction is further reduced by the synovial fluid. Articular cartilage consists of chondrocytes and two major macro-molecules; i.e., collagen and proteoglycans, which are synthesized by and deposited around the chondrocytes. The chondrocytes also synthesize the synovial fluid which bathes the articular cartilage.
The structural integrity of the articular cartilage is the foundation of optimal functioning of the skeletal joints in the hip, shoulders, elbows, hocks and stifles. Impaired function of skeletal joints will dramatically reduce mobility such as rising from sitting position or climbing and descending stairs. To maintain the structural integrity and the proper functioning of the articular cartilage, the chondrocytes constantly synthesize collagen and proteoglycans, the major components of the articular cartilage, as well as the friction-reducing synovial fluid. This constant synthesis of the macro-molecules and synovial fluid provides the articular cartilage with the repairing mechanism for most of the wearing caused by friction between the bone ends. However, it also leads to the constant demand for the supply of precursors, or building blocks, for the macromolecules and synovial fluid. Lack of this precursors will lead to defects in the structure and function of the skeletal joints. This deficiency occurs often when activity levels are very high, or cartilage tissue has been traumatized.
Degradation of the structures in articular cartilage is a typical characteristic of all diseases resulting in chronic destruction of the joint structures. Examples of such disorders are rheumatoid arthritis, psoriatic arthritis, and osteoarthrosis. Also, acute inflammation of a joint is often accompanied by destruction of the cartilage, although in most cases this will not develop into the chronically destructive disease. It is not known which factors are crucial for the acutely inflamed joint to either proceed to healing or develop into the chronic process. Examples of diseases involving acute joint inflammation are yersinia arthritis, pyrophosphate arthritis, gout arthritis (arthritis urica), septic arthritis and various forms of arthritis of traumatic etiology. Among other factors potentially conducive to the destruction of articular cartilage may be mentioned, for instance, treatment with cortisone; this has been known for a long time to accelerate the degenerative process in osteoarthrosis.
An adequate supply of metabolic precursors or building blocks is thus paramount to replacement and repair of the constituents of skeletal joints, connective tissue and synovial fluid. Proteoglycans (or mucopolysaccharides) form the ground substance of cartilage, bone and joint fluid. Proteoglycans are comprised of proteins linked to glycosaminoglycans (GAGS). The building block GAG subunit of the proteoglycan in cartilage and bone is chondroitin sulfate. Chondroitin sulfate A is present in cornea and cartilage. Chondroitin sulfate B (G-heparin) is found in tendon, aorta, skin and heart valves. Chondroitin C is found in cartilage, tendon and umbilical cord and similar tissues. The building block GAG subunit of the proteoglycan in joint fluid is hyaluronic acid. Intercellular solutions of hyaluronic acid are viscous and thus assist in lubrication of the joints of body skeleton. Hyaluronic acid is synthesized from the metabolic precursor, glucosamine. The availability of glucosamine in cartilage tissue can be rate-limiting to the enzymatic step leading to the production of proteoglycans. Exogenous glucosamine serves to drive the biosynthetic pathway forward past the rate-limiting blockage point. Glucosamine serves as a substrate for a kinase enzyme which yields glucosamine-6-phosphate, the rate-limiting precursor in proteoglycan synthesis.
Recently, studies have reported the suppression of autoimmune disorders such as rheumatoid arthritis upon ingestion of cartilage fibers derived from chickens and sharks. The therapy, termed oral tolerization, is not fully understood but it is theorized that a mechanism in the digestive tract disarms immune cells that would otherwise assault food molecules as foreign intruders to the body, akin to foreign substances that enter the blood stream by means other than the gastrointestinal tract. Apparently, the immune-disarming effect occurs not only in the gut, but also in the vulnerable tissues.
Also, it is well known that articular cartilage is composed of about 70% of water, chondrocytes and a cartilage matrix. The major components constituting the articular matrix are collagen and proteoglycan; the proteoglycan having good water retention characteristics is contained in the network of collagen having a reticulated structure. The articular matrix is rich in viscoelasticity and has an important role in reducing the stimulus and load imposed on the cartilage in order to maintain the normal morphology and function of the articular cartilage.
Osteoarthritis and rheumatoid arthritis are representative of the diseases accompanied by the destruction of the cartilage matrix. It is thought that the destruction of the matrix in these diseases is triggered by mechanical stresses with aging in the case of osteoarthritis and by excess proliferation of the surface layer cells of the synovial membrane, pannus formation and inflammatory cell infiltration in the case of rheumatoid arthritis, and both phenomena are caused through the induction of proteases. Since the degradation of articular cartilage is progressed in the extracellular region at a neutral pH, it is said that a matrix metalloprotease (hereinafter referred to as “MMP” or “MMPs” when used as the general term) whose optimal pH is in the neutral range plays a leading role in the degradation.
Numerous disclosures describe therapy of damaged tissues by introduction of precursors in the metabolic pathway leading to biosynthesis of the macromolecules of connective tissues. For example, in U.S. Pat. No. 3,697,652 (Rovati et al.), N-acetylglucosamine is used to treat degenerative afflictions of the joints. In U.S. Pat. No. 3,683,076 (Rovati et al.), glucosamine salts are described as pharmaceutically useful for treatment of osteoarthritis and rheumatoid arthritis. U.S. Pat. No. 4,647,453 (Meisner) and U.S. Pat. No. 4,772,591 (Meisner) disclose the use of glucosamine salts for treatment of degenerative inflammatory disease and as a means of accelerating wound healing. In U.S. Pat. No. 4,801,619 (Lindblad), a hyaluronic acid preparation is claimed to be effective for treatment of steroid arthropathy and progressive cartilage degeneration caused by proteoglycan degradation. A combination of glucosamine, chondroitin and manganese is claimed in U.S. Pat. No. 5,364,845 (Henderson) as a means of protecting and repair of connective tissue. None of these prior investigators, however, disclose a composition having metabolic precursors, herbal phytochemicals and palatability agents that work synergistically to prevent and treat joint and connective tissue disorders.
No medical cure exists for osteoarthritis. The progressive degeneration of the joint due to osteoarthritis is irreversible. Present therapies are directed to palliative medical therapies to reduce inflammation and pain and surgical therapies to reconstruct an affected joint or, in severe cases, to replace the joint with an artificial, prosthetic joint.
A need exists for an effective palliative medication for the treatment of osteoarthritis and other joint diseases which is both safe and effective when used for both short-term and long-term therapy and which can be administered orally.